The terms “K.O. drops” (“K.O. Tropfen” in German), “knockout drugs”, “roofies” or “date rape drugs” most often refer to GBH, also known as "liquid ecstasy" in the party scene. However there are also other, similar substances that are discreetly slipped into the drinks of unsuspecting women and men with the aim of making them unable to defend themselves. What exactly are knockout drops, and how do they work?